Excavating and load handling apparatus



Jan. 19, 1965 w. D. SYMMANK EXCAVATING AND LOAD HANDLING APPARATUS 2 Sheets-Sheet 1 Filed Aug. 2, 1963 FIG. I.

FIG.2.

INVENTOR. William D. Symmonk BY @Aw d;

ATTORNEYS Jan. 19, 1965 w. o. SYMMANK 3,165,205

EXCAVATING AND LOAD HANDLINGAPPARATUS Filed Aug. 2, 1963 2 Sheets-Sheet 2 FIG .4.

INVENTOR. William D. Symmonk BY M 1 HQ/M ATTORNEYS United States Patent HANDLING This invention relates to an apparatus for excavating and load handling and more specifically to suchan apparatus which is convertible to provide alternative modes of tool operation.

In general, although structural details vary widely, apparatus for excavating or load handling basically comprises a support structure, on which the operator is usually located, a boom pivotally attached at one end to the support structure, and a dipper stick pivotally attached at one end to the end of the boom. Hydraulic actuators swing the boom and dipper stick about their pivotal connections to the support structure and boom end, respectively. A tool of some sort is attached to the bottom end ofthe dipper stick. The term tool, as used here, refers to any device used for loading handling, or to any implement, such as a bucket or a blade, used for earth movbucket remainsfixed with respect to the dipper stick-dur ing the digging stroke, thus causing the bucket to swing in an arc, with the angle which the bucket face makes with a horizontal plane constantly changing. There are also in existence excavators which provide abucket stroke in which the bucket moves in a substantially horizontal direction, with thebucket facemaintaining a constant angle with respect to a horizontalplane. The latter type of motion is desirable, for instance, in forming the flat bottom of a ditch or swimming pool. It would be extremely useful to have a single piece of equipment which incorporated the two types of tool movement discussed.

It is accordingly an object of this invention to provide an excavating and load handling apparatus which may It is another 'object of this invention to provide such an apparatus in which the tool and other elements of the apparatusdo not have to be supported during the'convr vsion.--

These objectives are achieved, broadly, by pivotally attaching the .tool at spaced points to one end of the dipper stick and to one end of atool linkage. The other endgoti the tool linkage may be alternatively connected either to the dipper stick, for arcuate tool motion,'or to the boom, for a horizontal, constant-attitude stroke, The connection of the tool linkage may be easily changed. When it is connected to the dipper stick, the apparatus elerr'ients" may be so positioned thatthe tool linkage may be con-.

nected to the boorn before being'disconncted from; the dipper stick. Conversely, for the change dipper stickconnection.

ne d-ae ate t a b m The invention may, bef more clearlyunderstqodbyrefi erence "to the followin prej Patented Jan. 19, 1965 ferred embodiment of this invention in an excavator with a bucket used as the tool, taken in conjunction with the drawings, which form a part of the specification, and in which: a a 1 FIG. 1 is a side elevational view of a portion of an excavating apparatus embodying this invention, with the tool linkage being connected at one end to the'dipper stick structure, providing the apparatus with that mode of operation in which the bucket face swings in an arc with respect to the horizontal plane during the digging stroke;

FIG. 2 is a side elevational viewof a portion of the excavating apparatus of FIG; 1, with the vehicle base turned degrees, and with the elements of the apparatus being arranged in position to make the conversion from one mode of bucket movement to the other;

FIG. 3 is an enlarged view taken along line 33 of FIG. 2; and

FIG. 4 is a side elevational view of the excavating apparatus similar to that shown in FIG. 2, but with the tool linkage being connected at one end to the boom structure, providing that mode of operation in which the bucket maintains a constant attitude'with respect to a horizontal plane and moves along a horizontal line.

Turning now to FIG. 1, there is illustrated an embodiment of this invention in an excavating apparatus having a support structure lilwhich is mounted upon avehicle' equipped with tractor treads 12 and is rotatable about a vertical axis by means ofaturntable 11. A portion of a compressor 13 is shown attached to support structure 10. One end of an angled bottom structure 14 is'pivotally connected at :15 to support structure 10. At its other end, boom structure 14 is pivotally connected at 16 to the upper end of dipper stick structure 17. The lower end of dipper stick structure 17 is pivotally connected at 18 to bucket 19. 'Adouble-acting hydraulic boom actuator 22 is pivotally connected to support structure 10 at 23 and to boom structure 14 at 24. Two-additional bores 29 and 30, located in.the'middle of boom 14, provide alter native' points of pivotal attachment for the upper end of boom actuator 22, providing the equipment with three separate ranges of boom movement. A double-acting hydraulic dipper stick actuator 25 is pivotally connected at 26 to boom structure 14 and at 27 to the two rearwardly extending ears28 (only one ofwhich is visible in FIG. 1)

which form a part of dipper stick structure 17.

The tool linkage comprisesa double-active hydraulic tool actuator 31 anda tool arm 37, which are pivotally connected to each other at pivot point 34. The other end of tool actuator31 is pivotally connected at 32 to two forwardly extending ears 33 which form part ofdiP- per stick structure 17. The nature of the attachment of ears 33 to toolv actuator 31 maybe seen more clearly The other end of" tool armj37 is pivotally in FIG. 3. attached to bucket 19 at pivot point 38, which may be of a cross arm is pivotally attached at 34 to the joined ends of tool actuator 31 and toolarm 37, and the other end stem arm 35 is pivotally attached to dipper stick structure 17 at pivotlpoint 36 i A portion of tool actuator 31 extends upwardsbe yond I pivot point 32 and c ontains a bo re 41,which is unused in thisconfiguration. Two boom ears 42,1-both of which are visible in FIG. 3, form part of boom structure 14 and; each, of ears42j contains abore 43. Bores 43 are ieoaxial and are unus'ed-in the configurationof FIG. 1.

'Double acting" hydraulic actuators 22, ,25 and 3-1 are connected to. compressor 13 throughoperator manipumed. controls. andlhydrau lic lines, an of which are con;

ventional and none ,o ijwhich are shownon the drawinga,

attachedtool ii-s thus supported .th '1 at 3f2 while- 'the connection to boom ears 4:2 is beingrnade;

, 3- for purposes of simplicity. The actuatorsare independently operable The normal diggingstroke with the apparatus shown in FIG. 1 is made by extending dipper'stick'actuator 25* -so that dipper stick structure' 17 and bucket 19; move through anarc from the solidline positioninto the dot and there is no necessity for these heavy parts to be supported by the operator during the transition. 1

FIG. 4 shows a ground-scraping movement in which bucket 19 is moved along the surface 45 of the ground from the solid line position on the left to the dotted line position on the right, while the bucket face 44 is mainted line position or beyond'. Since the tool actuator 31- is normally operatedonly at the end; ofga stroke; tQ' pull the bucket up and prevent spillage whilernoyingthe boom, or to swing the bucket down and dump the on tents, the bucket will remainfixed with respect to dipper stick structure 17 during the normal digging stroke and therefore will swing in the are shown, with its face 44 changing in attitude with respect to a horizontal plane or to ground 45. The-purpose of breaking the toollinkage intoatwoarticulated, pivotally connected parts, tool,

actuator. 31, and tool arm 37;, and of proyidingthe additional, pivotally connected .cross arm 35, is .to permit more eflicient dumping of bucket 19.. The arrangement shown turns bucket 19- through 'a much greater clockwise are about pivot point 18 when tool actuator Slis extended, than, would bethe caseif thelowerend of tool actuator 3 were-directly connected to bucket 19.

Turning now to FIG. 2,. support structure is shown; rotated 90 degrees on turntable 11 from its position in FIG. 1 so that the tractor treads 12 are viewed end on and i the vehicle =46 to" which treads 12 are attached may be seen. "Theexcayator elements have been arranged to permit conversion from the type "of operation shown in FIG.

l, infwhichthe bucket swings in an arc, to the type of 1 operation shown lFIG. 4, infwhichthe bucket moves essentially parallel to a horizontal plane or to the sur-;

face 45 of the earth. Dipperjstick actuator is' fully extended and tool actuator 31 fullyretract'ed,=resulting in the alignment-of bore. slat-the end of tool'jactuator 3'1 withbores 43 at the end of boom ears 42.1 The fact that this bore alignment which isrequired for transition is achievedby full extension of one independentlyoperable cylinder .and the full retraction of another independently operable'cylinder provides great convenience to alignment from his position on the equipment, without the necessity of close personal observation of the cooperating parts and without the necessity of painfully inching; the parts into their correct relationship.

' The-relationship ofthe various bores to each other and' the nature of the .connections' made and unmade in this transition mayibese'enrnore' clearlyin the enlarged view of FIG. 3. -When bores 41' and'43areaxially alignedzby.

full extension of dipper'stick actuator 25-and full retraction of tool actuator 31, a pin51 having anenlarged head 52 atone endis driven through bores 41 and 43 and may be securedfrom withdrawal by means of acotter pin 53 or the like. This connects tool actuator 31 to boom ears 4 2 of. boom structu'reil t inaddition to fears 33 of dipper stick structure 17, asshown' in FIGS: 2.and 31 All that I remains to complete thetrans'ition is to remove pin'54 which still remains inserted'through bores 56 inears' 33 andborezSS in tool actuator 31, and therefore snu'cerr nects theltool actuator to the dipper stick structure. 7 Pin 54 is similar'to pin 51 already described, having. an en-f largedhead 57 at one 'ehd and beingre'tainedagainst withdrawal at the-other end by a. cotter pin 5 S or the like. Dnce cotter pin '58. is ren oved and pin ss'withdra'wn,

toolactuator 31 is disconnected from the. dipper stick 'tained at a substantially constant angle with respect to :points of pivotal attachmentof the tool; that is,'the distance between pivotal connection points .13 and 38 on bucket 19, tor-ms one side of a rough, parallelogram. The opposite side of this parallelogram is formed by the distance between the pivotal connections of the dipper stick structure and the tool actuator on .thelyboorn structure, or between pivotal points 16 and el, 43 on boom structure 14.

" The other two sides of the rough parallelogram are dipper the tool linkage side is broken into two ar'ticuiated sections stick structure 17 and the tool linkage, which; comprises tool actuator 31 and tool arm 37 towhich it is connected. While this is far from being a true parallelogram because and because of the addition ofthe. pivoted cross arm 35,

still it does function .ro'ughly'as a parallelogram, maintaiir ing its opposed sides parallel no matter how the sides are pivoted about the vertices. Thus as dipper stick structure 17 ispivoted about point leby actuator 25, bucket 1'3 will tend to maintain a constantfattitudewith'respect to boom .struoture 1 4; and if boom structure '14'r'emains stationary and at the appropriate angle, the face 44 of bucket 19 may be maintained at a desired angle with respect to i the ground surface the operator, in that he is able ,to achieve accurate bore There is a modificationyto. this parallelogram vmotion, however. As dipper'stick structural? is swung about pivot point 1 6, bucket 19, tends toyride upwards, away from groundsurfac'e 45 For thisreason, boom struc-' ture 14 must-be lowered during the stroke (see the dotted line position in FIG. 4) to maintain bucket 19. in" a horizontal path. This clockwise motion of boom structure ltabout pivot'p'oint 15..will tend'to alter the attitude of bucketl? by causing it to turn in a-clockwise direction with respect to the ground 'surface 45. To compensate for this, and maintain the bucketattitude; constant with respect to the ground, .the' parallelogram configuration is deliberately distorted fromthat of a true parallelogram by making the topside, the distance alongcthc boonr structure between pivot points '16 andsl, 43, smaller than thelbottom side, the distance along the. top of bucket 19 7 between pivotypoints. 18'and 38. Thus, bucket 19 does not form one side of a true parallelogram, and: will not remain precisely parallelto itsiopposite' side as. theifconfiguration of the rough parallelogram is changed. Rather, as dipper. stick actuator '25=is extended," sw g g pp stick structure 17 counterclockwise about its pivotal -x nection 16 with boom structure 14, the deviation from a true parallelogramlwill cause bucketlfi. to turn slight y.

Counterclockwise with respect" to boom structure 1 5.

structure, vresulti'rigin the appropriateconfiguration. for I the apparatus to describe the generally}; horizontal tool, movement shown in FIG.'4.

- lt will tbe @P-paient that one rune advantages ti; s

dipper stick 'u'ct-ure; Theentireas's'en lyof linkages and i'vota'l connections O I nvention 1s that'it permits 'thetoolilmkage t-obe connected to the" boom "structure while' it is 'still. connected to the This offsetsthe opposite effect on {the attitudeof bucket 19 caused byythe lowering. of" boom 14,10 that in the 1 combined ground-scraping operationfwherein dipper Stickactuator ZS'is eXtendedI'andboom actuator 22 is re.- itractedto lowefiboomstrUc-ture 14-,"the total effect upon l Ql 19 will .be;:to rn'ove itaslshown in'PlG: from the; solid line position; to the dotted lineposition al ng 8;. f n amaa t l s wseaT 11 Pr j ct. it m/ rm de'grjeat r than the: 1

largest dimension of tool cylinder 31 in that direction so that the tool actuator is free to pass between cars 33 as shown in the solid line position of FIG. 4.

The excavating apparatus of this embodiment is easily convertible from the horizontal tool movement configuration shown in FIG. 4 to the arcuate tool movement configuration shown in FIG. 1. This is accomplished by fully extending dipper stick actuator 25, and fully retracting tool actuator 31 to achieve the physical configuration shown in FIGS. 2 and 3. The conversion is then made by reversing the process for conversion from arcuate tool motion to horizontal tool motion. In making the conversion from the horizontal motion configuration to the arcuate configuration, once bore 55 in tool actuator 31 has been aligned with bores 56 on ears 33 which project forwardly from dipper stick structure 17, pin 54 is inserted through those bores and pin 51 subsequently withdrawn from bores 41 and 43.

While the preferred embodiment of the invention has been described, various modifications may be made while remaining withinthe scope of the invention, some of which are indicated below.

While hydraulic cylinders are used herein for power actuators 22, 25 and 31, any other power device may be used which is capable of rotating the corresponding elements.

The tool linkage may be a single member, rather than the two pivoted, articulated members used in the preferred embodiment. In fact, depending upon the nature of the tool to be used, the tool linkage need not, for purposes of this inventive concept, be of adjustable length at all. It is conceivable that it be a single, rigid member of constant length, capable of being connectedat its upper end either to the boom structure or to the dipper stick structure. I

It is not necessary that the proper alignment of the bores for transition from one mode of operation to the other require the full extension of the actuator for the dipper stick structure and the full retraction of the tool actuator. The apparatus may be adjusted so that the proper bore alignment results from any predetermined settings of the appropriate elements.

Other alterations and modifications of the preferred embodiment as may suggest themselves to those skilled in the art are within the scope of the invention, which is defined only by the claims.

What is claimed is:

1. An excavating apparatus comprising the combination of:

support means; i

a boom structure pivotally mounted upon said support means for motion about a first horizontal axis; first power means operatively attached to said boom structure to swing said boom structure about said first horizontal axis;

a dipper stick structure pivotally mounted upon said boom structure for motion about a second horizontal axis;

second power means operatively attached to said dipper stick structure to swing said dipper stick structure about said second horizontal axis;

a tool structure pivotally mounted upon said dipper stick structure for motion about a third horizontal axis;

a linkage having two ends,

one of said ends of said linkage being pivotally connected to said tool structure at a point spaced from said third horizontal axis,

first pivotal attaching means for pivotally attaching the other of said ends of said linkage to said dipper stick structure, and

second pivotal attaching means for alternatively pivotally attaching said other of said ends of said linkage to said boom structure at a point spaced from said second horizontal axis,

6-: whereby, by said alternative attaching means there is made available two alternative patterns of tool structure motion when said dipper stick structure is swung about said second horizontal axis. 2. An excavating apparatus comprising the combination of:

support means; a boom structure pivotally mounted upon said support means for motion about a first horizontal axis; first power means operatively attached to said boom structure to swing said boom structure about said.

first horizontal axis;

a dipper stick structure pivotally mounted upon said boom structure for motion about a second horizontal axis;

second power means operatively attached to said dipper stick structure to swing said dipper stick structure about said second horizontal axis;

a tool structure pivotally mounted upon said dipper stick structure for motion about a third horizontal axis;

a poweroperated linkage of adjustable length, having two ends, and being adapted to swing said tool structure about said third horizontal axis as a result of alteration in its length,

one of said ends or" said linkage being pivotally connected to said tool structure at a point spaced from said third horizontal axis, first pivotal attaching means for pivotally attaching the other of said ends of said linkage to said dipper stick structure, and second pivotal attaching means for alternatively pivotally attaching said other of said ends of said linkage to said boom structure at a point spaced from said second horizontal axis,

l whereby, by said alternative attaching means there is made available two alternative patterns of tool structure motion when said dipper stick structure is swung about said second horizontal axis.

3.An excavating apparatus comprising the combination of:

support means;

a boom structure pivotally mounted upon said support means for motion about a first horizontal axis;

first power means operatively attached to said boom structure to swing said boom structure about said first horizontal axis;

a dipper stick structure pivotally mounted upon said boom structure for motion about a second horizontal axis; 7

second power means operatively attached to said dipper stick structure to swing said dipper stick structure about said second horizontal axis; a tool structure pivotally mounted upon said dipper stick structure for motion about a third horizontal axis; a linkage having two ends,

one of said ends of said linkage being pivotally connected to said tool structure at a point spaced from said third horizontal axis,

said linkage being provided with first and second pivotal connecting elements adjacent the other of said ends;

said boom structure being provided with a third pivotal connecting elements spaced from said second'horizontal axis; said dipper stick structure being provided with a fourth pivotal connecting element;

said first and fourth pivotal connecting elements being operatively engaged, whereby said other end of said linkage is pivotally connected to said dipper stick structure;

said boom structure, said dipper stick structure,

I 4. The apparatus of claim 3 in which said linkage comprises a power operated linkage of adjustable length, being adapted to swing said tool structure about said third horizontal axis as a result of alteration in its length; v

said second power means comprises a power operated actuating arm of adjustable length; and

wherein the disposition of said boom structure, said dipper stick structure, and said linkage with respect to each other so that said second and third pivotal connecting elements may be operatively engaged is accomplished by the adjustment of said linkage and said second power means to predetermined lengths. 5. The apparatus of claim 4 in which .said linkage and said second power means bothcomprise double-acting hydraulic cylinders;

said predetermined length of said linkage comprises its shortest length with its hydraulic cylinder fully retracted; and

said predetermined length of said second power means comprises'its longest length with its hydraulic cylinder fully extended.

6. An excavating apparatus comprising the combination of:

support means;

a boom structure pivotally mounted upon said support means for motion about a first horizontal axis;

first power means operatively attached to said boom structure to swing said-boom structure about said first horizontal axis;

a dipper stick structure pivotally mounted upon said boom structure for motion about a second horizontal axis;

second power means operatively attached to said dipper stick structure to swing said dipper stick structure about said second horizontal axis;

a tool structure pivotally mounted upon said dipper stick structure for motion about a third horizontal axis;

a linkage having two ends,

one of said ends of said linkage being pivotally connected to said tool structure at a pointspaced from said third horizontal axis, said linkage being provided with first and second pivotal connecting elements adjacent the-other of saidends;

said boom structure being provided with a third pivotal said other end of said linkage is pivotally connected to said dipperstick structure and disconnected from said boom structure.

I 7. The apparatus of claim 6 in which said linkage comprises a power operated linkage of 8 adjustable length being adapted to swing said tool structure about said third horizontal axis as a result of alteration in its length; said second power means comprises a power operated actuating arm of adjustable length; and I wherein the disposition of said boom structure, said dipper stick structure, and said linkage with respect.

to each other so that said first andfourth pivotal connecting elements may be operatively engaged is accomplished by the adjustment of said linkage and said second power means to predetermined lengths.

8. The apparatus of claim 7 in which said linkage and said second power means both com-- prise double-acting hydraulic cylinders;

said predetermined length of said linkage comprises itsshortest length with its hydraulic cylinder fully retracted; and

said predetermined length of said second power means comprises its longest length with its hydraulic cylinder fully extended.

9. An excavating apparatus comprising the combination of I support means;

a boom structure pivotally mounted upon said support means for motion about afirst horizontal axis;

first power means operatively attached to said boom structure to swing said boom structure about said first horizontal axis;

a dipper stick structure pivotally mounted upon said bottom structure for motion about a second horizontal axis;

second power means operatively attached to said dip-.

per stick structure to swing said dipper stick structure about said second horizontal axis;

' g a tool structure pivotally mounted upon said dipper connected to; said tool structure at a point.

, spaced from said third horizontal axis, said linkage being provided with first and second bores adjacent the other of said ends;

'said boom structure being provided with a third bore spaced from second horizontal axis;

said dipper stick structure being provided with a fourth bore;

said first and fourth bores being axially. aligned and having a pin inserted therethrough,whereby said other end of said linkage is pivotally connected to said dipper stick structure;

said boom structure, said dipper stick structure, and said linkage being adapted to be so disposed with respect-"to each other that said secondand third bores are axially aligned, whereby a pin may be inserted through them and said pin removed from said first and fourth bores, thereby converting said apparatus from one mode of tool motion. to another. i

10. The apparatus of claim 9 in which said linkage comprises a power operatedlinkage of ad justable'length being adapted to swing said tool structure about said'third horizontal axis as a result of alteration in its length;

said second power means comprises a power operated actuating arm of adjustable length; and

wherein the disposition of said boom structure, said 7 dipper stick structure, and said linkage with respect 'to each other so that said second and third bores are axially aligned is accomplishedby the adjustment of said linkage and said second power means to predetermined lengths.

' ii. The apparatus of claim 10 in which said predetermined length of said linkage comprises its shortest length with its hydraulic cylinder fully retracted; and

said predetermined length of said second power means comprises its longest length with its hydraulic cylinder fully extended.

12. An excavating apparatus comprising the combination of:

support means;

a boom structure pivotally mounted upon said support means for motion about a first horizontal axis;

first power means operatively attached to said boom structure to swing said boom structure about said first horizontal axis;

a dipper stick structure pivotally mounted upon said boom structure for motion about a second horizontal axis;

second power means operatively attached to said dipper stick structure to swing said dipper stick structure about said second horizontal axis;

a tool structure pivotally mounted upon said dipper stick structure for motion about a third horizontal axis;

a linkage having two ends,

one of said ends of said linkage being pivotally connected to said tool structure at a point spaced from said third horizontal axis,

said linkage being provided with first and second bores adjacent the other of said ends;

said boom structure being provided with a third bore spaced from said second horizontal axis;

said dipper stick structure being provided with a fourth bore;

said second and third bores being axially aligned and having a pin inserted therethrough, whereby said other end of said linkage is pivotally connected to said boom structure;

said boom structure, said dipper stick structure, and

said linkage being adapted to be so disposed with respect to each other that said first and fourth bores are axially aligned, whereby a pin may be inserted through them and said pin removed from said second and third bores, thereby converting said apparatus from one mode of tool motion to another.

13. The apparatus of claim 12 in which said linkage comprises a power operated linkage of adjustable length being adapted to swing said tool structure about said third horizontal axis as a result of alteration in its length;

said second power means comprises a power operated actuating arm of adjustable length; and

wherein the disposition of said boom structure, said dipper stick structure, and said linkage with respect to each other so that said first and fourth bores are axially aligned is accomplished by the adjustment of said linkage and said second power means to predetermined lengths.

14. The apparatus of claim 13 in which said linkage and said second power means both comprise double-acting hydraulic cylinders;

said predetermined length of said linkage comprises its shortest length with its hydraulic cylinder fully retracted; and

said predetermined length of said second power means comprises its longest length with its hydraulic cylinder fully extended.

References Cited in the file of this patent UNITED STATES PATENTS 2,813,645 Pilch Nov.19, 1957 

1. AN EXCAVATING APPARATUS COMPRISING THE COMBINATION OF: SUPPORT MEANS; A BOOM STRUCTURE PIVOTALLY MOUNTED UPON SAID SUPPORT MEANS FOR ROTATION ABOUT A FIRST HORIZONTAL AXIS; FIRST POWER MEANS OPERATIVELY ATTACHED TO SAID BOOM STRUCTURE TO SWING SAID BOOM STRUCTURE ABOUT SAID FIRST HORIZONTAL AXIS; A DIPPER STICK STRUCTURE PIVOTALLY MOUNTED UPON SAID BOOM STRUCTURE FOR MOTION ABOUT A SECOND HORIZONTAL AXIS; SECOND POWER MEANS OPERATIVELY ATTACHED TO SAID DIPPER STICK STRUCTURE TO SWING SAID DIPPER STICK STRUCTURE ABOUT SAID SECOND HORIZONTAL AXIS; A TOOL STRUCTURE PIVOTALLY MOUNTED UPON SAID DIPPER STICK STRUCTURE FOR MOTION ABOUT A THIRD HORIZONTAL AXIS; A LINKAGE HAVING TWO ENDS, ONE OF SAID ENDS OF SAID LINKAGE BEING PIVOTALLY CONNECTED TO SAID TOOL STRUCTURE AT A POINT SPACED FROM SAID THIRD HORIZONTAL AXIS, FIRST PIVOTAL ATTACHING MEANS FOR PIVOTALLY ATTACHING THE OTHER OF SAID ENDS OF SAID LINKAGE TO SAID DIPPER STICK STRUCTURE, AND SECOND PIVOTAL ATTACHING MEANS FOR ALTERNATIVELY PIVOTALLY ATTACHING SAID OTHER OF SAID ENDS OF SAID LINKAGE TO SAID BOOM STRUCTURE AT A POINT SPACED FROM SAID SECOND HORIZONTAL AXIS, WHEREBY, BY SAID ALTERNATIVE ATTACHING MEANS THERE IS MADE AVAILABLE TWO ALTERNATIVE PATTERNS OF TOOL STRUCTURE MOTION WHEN SAID DIPPER STICK STRUCTURE IS SWUNG ABOUT SAID SECOND HORIZONTAL AXIS. 